The present invention relates to a variable displacement swash plate type compressor for use as a refrigerant compressor of, for example, an automotive air conditioner and, more particularly, a variable displacement swash plate type compressor which reduces vibration and noise generated during operation of the compressor.
Variable displacement swash plate type compressors for automotive air conditioners are shown, for example, in Japanese Patent Publication No. 58-4195 and Japanese Unexamined Utility Model Publication No. 61-142184 and Unexamined Patent Publication No. 61-286591. Each of these known variable displacement swash plate type compressors includes a main shaft to which driving torque is transmitted from an automotive engine, a driving pin or a driving ring fixed to the shaft, a link mechanism or a cam mechanism engaging with the driving pin or the driving ring, a swash plate which changes its angle of tilt with respect to the main shaft by the operation of the link mechanism or the cam mechanism and is capable of making a precessional rotation, and pistons which engage the swash plate so as to be reciprocatingly driven by the precessional rotation of the swash plate.
During operation of this known compressor, an unbalance of centrifugal force is produced by the rotation of the compressor shaft and rotational parts as the sum of unbalance of centrifugal force acting on the driving pin or the driving ring and the unbalance of centrifugal force acting on the swash plate. Another unbalance of centrifugal force is also caused when the position of the center of gravity of a rocker plate, engaged with the swash plate to make a precessional rotation together with the swash plate, is spaced from the center of tilt of the swash plate. The extent or magnitude of the unbalance of centrifugal force acting on the driving pin or the driving ring is determined independently of the tilting angle of the swash plate. On the other hand, the magnitudes of the unbalance of centrifugal forces acting on the swash place and the rocker plate vary in dependence upon the distances of the centers of gravity of component parts of the swash plate and the rocker plate which in turn vary according to the angle of tilt of the swash plate. Consequently, the overall unbalance of the centrifugal force, synthesized from the unbalance components mentioned above, vary according to the angle of tilt of the swash plate even when the speed of rotation is unchanged. Thus, the magnitude of the overall unbalance of the centrifugal force varies according to the angle of tilt of the swash plate, so that a large unbalance is produced when the tilting angle is maximum, i.e., when the displacement is maximized, or when the tilting angle is minimum, i.e., when the displacement is minimized. This unbalance of centrifugal force causes a vibration of the compressor to generate large vibration and noise of the internal and external parts of the automobile. This problem is serious particularly when the engine is idling.